In presently known microprocessors and, more particularly, in single chip microprocessors, data entered therein is safeguarded by physically breaking the data bus lines which are externally accessible and which are no longer required for further data input. Such a physical interruption of the data bus lines is extremely difficult to carry out, particularly in the case of encapsulated chips. Diamond drills are required for this purpose. These drill through the chip at the corresponding location so that the output lines are broken. A microprocessor which has been treated in this manner cannot be re-used for a different purpose.